Disk drives are widely used in computers and data processing systems for storing information in digital form. In conventional Winchester type disk drives, a slider “flies” upon an air bearing or cushion in very close proximity to a storage surface of a rotating data storage disk. A data transducer is secured to the slider. The storage surface carries a thin film of magnetic material having a multiplicity of magnetic storage domains that may be recorded and read back by the data transducer. Preferably, the storage surface is smooth so that the slider can fly relatively close to the storage surface to maximize data transfer accuracy.
For a multiple disk, disk drive, a plurality of sliders are supported near the storage surfaces of the storage disks with a plurality of actuator arms. More specifically, each slider is secured to one actuator arm with a load beam and a head suspension having a suspension gimbal. Typically, an actuator motor moves the actuator arms along a predetermined path to position the sliders relative to the storage surfaces of the storage disks. The combination of the sliders, the load beams, the head suspensions, the actuator arms, and the actuator motor are commonly referred to as a head stack assembly.
FIG. 1A illustrates a prior art head suspension 10P, slider 12P and a storage disk 14P. In this embodiment, the slider 12P has a positive pitch static angle 16P. The pitch static angle 16P defines the free angle formed between the slider 12P and the horizontal when the suspension 10P is held so that the slider 12P is positioned at the normal flying height above the storage disk 14P.
The air bearing which enables each slider to fly in close proximity to the surface of the disks, is created by air flow generated by rotation of the disks. When the disk rotation ceases, the air bearing dissipates and the sliders are no longer supported above the surfaces of the disks. Thus, when power is removed from a spindle motor that rotates the storage disks, the sliders come to “rest” or “land” on the surfaces of the disks. Likewise, when the spindle motor is powered up, the sliders “take off” from the surfaces of the disks. When the slider is at rest on the surface of a disk, a static frictional force (“stiction”) arises between the slider and the disk. The stiction can lead to loss of data and/or failure of the disk drive due to erosion or scarring of the magnetic film on the surfaces of the disks. Alternately, the stiction may prevent the spindle motor from spinning the disks and/or may cause the data transducer to fail.
In some disk drives, the actuator motor positions each slider over a landing zone as power is removed from the spindle motor. This inhibits the slider from resting on an area of useful data storage during non-rotation of the storage disk. Further, the landing zone is typically textured to minimize striction between the slider and the storage disk at the landing zone.
Alternately, in a ramp-type disk drive, the actuator motor moves the sliders radially outward so that each head suspension slides onto a ramp positioned near an outer diameter of the storage disks. In this position, each slider is “unloaded” from the storage disks.
Still alternately, some disk drives are designed with padded sliders that rest on the smooth storage surface when disk rotation ceases. Referring to FIG. 1A, a typical padded slider 12P includes an air bearing surface 18P with one or more pads 20P which are positioned closer to the storage disk than the air bearing surface 18P. The pads 20P of a “padded” slider 12P help to minimize the contact between the slider 12P and the disk 14P. This, in turn, helps to minimize striction and the potential for damage that may occur to the disk drive or any of its elements during the shut down or start up phases of operation.
Unfortunately, padded sliders 12P can be prone to rotate and/or tip off their pads 20P when the slider 12P comes to rest on the storage disk 14P. The predominant driving force for tipping is friction that acts during backward disk 14P rotation, which can occur if the motor cogs, or under the influence of external rotational shock. This friction acts at the slider 12P/disk 14P interface and provides a moment that acts to tip the slider 12P off its pads 20P. Referring to FIG. 1B, the tipping brings the non-padded portion of the air bearing surface 18P near the back of the slider 12P in contact with the disk 14P. Unfortunately, the contact area between slider 12P and the disk 14P and stiction increase dramatically with the slider 12P in the tipped condition.
On attempt to solve the problem of slider tipping is to locate the trailing pads close to the trailing edge of the slider and moving the load point toward the slider leading edge. This reduces the friction between the slider and the disk. Unfortunately, the distance between the trailing edge and the trailing pads is also constrained by flying height clearance of the slider. More specifically, the extent to which the trailing pads can be moved to the trailing edge is limited by the requirement that the trailing edge pads clear the disk when the drive is operating at full speed. Generally, the farther back the pads are placed, the less likely they are to clear the disk under all full speed circumstances. Therefore, this method is not completely satisfactory.
In light of the above, it is an object of the present invention to provide a reliable, simple, and efficient device which effectively protects the disks and the sliders during shut down and start-up of a disk drive. Still another object of the present invention is to increase the reliability of any disk drive that employs padded slider technology. Yet another object of the present invention is to provide a disk drive which is relatively easy and cost effective to manufacture, assemble and use.